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sys.sp_query_store_set_hints (Transact-SQL)

  • Článek

Applies to: SQL Server 2022 (16.x) Azure SQL Database Azure SQL Managed Instance

Creates or updates Query Store hints for a given query_id.

Transact-SQL syntax conventions

Syntax

sp_query_store_set_hints
    [ @query_id = ] query_id ,
    [ @query_hints = ] 'query_hints'
    [ , [ @query_hint_scope = ] 'replica_group_id' ]
[ ; ]

Arguments

[ @query_id = ] query_id

The Query Store query_id column from sys.query_store_query. @query_id is bigint.

[ @query_hints = ] N'query_hints'

A character string of query options beginning with OPTION. @query_hints is nvarchar(max). For more information, see Supported query hints in this article.

[ @query_hint_scope = ] 'replica_group_id'

By default, the scope of a new Query Store hint is the local replica only. @query_hint_scope is tinyint. This optional parameter determines the scope at which the hint will be applied on a secondary replica when Query Store for secondary replicas is enabled. The optional query_hint_scope argument defaults only to the local replica (primary or secondary), but you can optionally specify a replica_group_id referencing sys.query_store_replicas.

Return value

0 (success) or 1 (failure).

Remarks

Hints are specified in a valid T-SQL string format N'OPTION (..)'.

  • If no Query Store hint exists for a specific query_id, a new Query Store hint will be created.
  • If a Query Store hint already exists for a specific query_id, the last value provided will override previously specified values for the associated query.
  • If a query_id doesn't exist, an error will be raised.

In the cases where a hint would cause a query to fail, the hint is ignored and the latest failure details can be viewed in sys.query_store_query_hints.

To remove hints associated with a query_id, use the system stored procedure sys.sp_query_store_clear_hints.

Supported query hints

These query hints are supported as Query Store hints:

{ HASH | ORDER } GROUP
  | { CONCAT | HASH | MERGE } UNION
  | { LOOP | MERGE | HASH } JOIN
  | EXPAND VIEWS
  | FAST number_rows
  | FORCE ORDER
  | IGNORE_NONCLUSTERED_COLUMNSTORE_INDEX
  | KEEP PLAN
  | KEEPFIXED PLAN
  | MAX_GRANT_PERCENT = percent
  | MIN_GRANT_PERCENT = percent
  | MAXDOP number_of_processors
  | NO_PERFORMANCE_SPOOL
  | OPTIMIZE FOR UNKNOWN
  | PARAMETERIZATION { SIMPLE | FORCED }
  | RECOMPILE
  | ROBUST PLAN
  | USE HINT ( '<hint_name>' [ , ...n ] )

The following query hints are currently unsupported:

Permissions

Requires the ALTER permission on the database.

Examples

Identify a query in Query Store

The following example queries sys.query_store_query_text and sys.query_store_query to return the query_id for an executed query text fragment.

In this example, the query we're attempting to tune is in the SalesLT sample database:

SELECT * FROM SalesLT.Address as A
INNER JOIN SalesLT.CustomerAddress as CA
on A.AddressID = CA.AddressID
WHERE PostalCode = '98052' ORDER BY A.ModifiedDate DESC;

Query Store doesn't immediately reflect query data to its system views.

Identify the query in the Query Store system catalog views:

SELECT q.query_id, qt.query_sql_text
FROM sys.query_store_query_text qt
INNER JOIN sys.query_store_query q ON
    qt.query_text_id = q.query_text_id
WHERE query_sql_text like N'%PostalCode =%'
  AND query_sql_text not like N'%query_store%';
GO

In the following samples, the previous query example in the SalesLT database was identified as query_id 39.

Apply single hint

The following example applies the RECOMPILE hint to query_id 39, as identified in Query Store:

EXEC sys.sp_query_store_set_hints @query_id= 39, @query_hints = N'OPTION(RECOMPILE)';

The following example applies the hint to force the legacy cardinality estimator to query_id 39, identified in Query Store:

EXEC sys.sp_query_store_set_hints @query_id= 39, @query_hints = N'OPTION(USE HINT(''FORCE_LEGACY_CARDINALITY_ESTIMATION''))';

Apply multiple hints

The following example applies multiple query hints to query_id 39, including RECOMPILE, MAXDOP 1, and the SQL 2012 query optimizer behavior:

EXEC sys.sp_query_store_set_hints @query_id= 39, @query_hints = N'OPTION(RECOMPILE, MAXDOP 1, USE HINT(''QUERY_OPTIMIZER_COMPATIBILITY_LEVEL_110''))';

View Query Store hints

The following example returns existing Query Store hints:

SELECT query_hint_id, query_id, query_hint_text, last_query_hint_failure_reason, last_query_hint_failure_reason_desc, query_hint_failure_count, source, source_desc
FROM sys.query_store_query_hints
WHERE query_id = 39;

Remove the hint from a query

Use the following example to remove the hint from query_id 39, using the sp_query_store_clear_hints system stored procedure.

EXEC sys.sp_query_store_clear_hints @query_id = 39;

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